[SAC-HELP] plotting problem

["LANGLAUDE Philippe - CETE Méditerr./LABO NICE/RISQUE NATUREL - GEOLOGIE"]

Thank you very much for SAC which is very hepfull for our team.
We have a question:

1) we compute 4 spectra (a b c d) with FFT command
these spectra have the same frequency delta.
2) then we divide spectrum "a" by spectrum "b"
the result is noted "E"
3) and we divide  spectrum "c" by spectrum "d"
the result is noted "F"
4) Now we want to plot E only for frequencies where F is >3
...
How to do that last operation ?


Philippe Langlaude
------------------------------------------------------------------
Equipe de Recherche "Risques Sismiques"            CETE méditerranée
*  Laboratoire de Nice 56 bd Stalingrad  F-06359 Nice cedex 4 France
*  06 24 83 34 04   /  (33) 04 92 00 81 67   *   (33) 04 92 00 81 39
*  Philippe.Langlaude at i-carre.net
http://www.cete-mediterranee.fr